The School of Earth and Atmoshperic Sciences Presents Dr. Frances Rivera-Hernandez, Dartmouth University

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A School of Earth and Atmospheric Sciences Presents Dr. Eric O. Lindsey, Nanyang Technical University

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The School of Earth and Atmospheric Sciences Presents Dr. Behrooz Ferdowski, Princeton University

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The School of Earth and Atmospheric Sciences Presents Dr. Hao Cao, Harvard University

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The School of Earth and Atmospheric Sciences Presents Dr. Christopher Milliner, NASA Jet Propulsion Laboratory

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The School of Earth and Atmospheric Sciences Presents Dr. Matthew Siegler, NASA Jet Propulsion Laboratory

 Dr. Matthew Siegler will provide an overview of ongoing and future geothermal heat flow projects on the Moon and Mars. We will look at the recently landed InSight mission, new analysis of Apollo heat flow data, Orbital microwave-wavelength measurements, and a dawning era of or subsurface planetary exploration and planetary geophysics.

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The School of Earth and Atmospheric Sciences Presents Dr. Elvira Mulyukova, Yale University

Grain Scale Physics of Plate Boundaries: Tectonic Processes from Geological to Human Time Scales

 The motion of tectonic plates along our planet’s surface shapes the relationship between the solid Earth and its surrounding elements, including the atmosphere, ocean, and life. 

Examples include the chemical reactions between minerals and water at seafloor spreading centers, as well as volcanic degassing at subduction zones, both of which link plate tectonics to the global volatile cycles. Furthermore, volcanism and seismicity along plate boundaries have a clear impact on human life. 

However, Earth is enigmatic in that it is the only known terrestrial body that has plate tectonics. Understanding how plates and plate boundaries form and evolve is fundamental to our understanding of the Earth system as a whole. 

In order for a new tectonic plate to form, the cold and stiff oceanic lithosphere must be weakened sufficiently to deform at tectonic rates. The weakening mechanisms involve the microscale physics of mineral grains and their control on the strength of the lithosphere. 

In this talk, I will present the microphysics of lithospheric weakening by mineral grain size reduction, known as grain damage, and its application to tectonic scale processes, such as subduction initiation. 

I will also present the newly developed theory of grain mechanics, which couples evolution of grain size and intragranular defects. The new model predicts oscillations in grain size, and possibly material strength, on a time scale that is relevant to earthquake cycles and postseismic recovery, thus connecting plate boundary formation processes to the human time scale.

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The School of Earth and Atmospheric Sciences Presents Dr. Laura Stevens, Columbia University

Mass loss from the Greenland Ice Sheet contributes a quarter of today’s global sea level rise. Roughly half of this Greenland Ice Sheet mass loss is derived from accelerated flow of the ice sheet due in part to the ability of surface meltwater to access, lubricate, and enhance sliding along the ice-bed interface. 

Determining the processes that govern the ice sheet’s dynamic flow response to increased surface meltwater production is critical for understanding how ice sheets work and predicting how ice sheets will behave in our warming climate. 

This talk will examine the influence of meltwater on two regimes of Greenland Ice Sheet flow: (1) rapid supraglacial lake drainages in the slowly-flowing inland margin, and (2) diurnal meltwater influences on fast-flowing marine-terminating outlet glaciers. 

A combination of Global Positioning System (GPS) observations of ice-sheet surface displacement, inverse methods, and time series analysis will be used to investigate these processes.

In the slow-flowing regime, rapid supraglacial lake drainages provide an ideal natural experiment that enables us to probe the upper limits of meltwater’s influence on ice-flow acceleration. These lake drainages are spectacular events, where hydro-fractures—water-driven crevasses—drain ~3-km diameter lakes from the surface to the bed of the ice sheet in a matter of hours at rates equivalent to the discharge across Niagara Falls. 

This half of the talk will investigate what triggers rapid lake drainage using a Network Inversion Filter (NIF) to invert a dense, local network of GPS observations during three lake drainage events.

In the fast-flowing regime, marine-terminating outlet glaciers are the gatekeepers of the inland ice sheet’s access to the sea. The dynamics of these glaciers are governed by complex interactions between the atmosphere, ocean, and ice-sheet bed. 

This half of the talk will investigate how atmospheric and oceanic forcing influence short-term (hourly) variations in horizontal flow of Helheim Glacier, East Greenland as observed by an array of GPS receivers. Improved mechanistic understanding of how tidal and atmospheric forcing drive marine outlet glacier flow is critical for determining how rapidly ice will be discharged into the ocean as these regions warm.

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The School of Earth and Atmospheric Sciences Presents Dr. Wing Yin "Winnie" Chu, Stanford University

The last decade has seen significant advancements in our understanding of ice sheet hydrology and in particular, the role of subsurface drainage hidden within and beneath the ice sheets. 

Radar sounding is one of the few unique geophysical tools that allow us to image and constrain processes occur in these traditionally difficult-to-observe subsurface environments. Nonetheless, despite their usefulness, robust analysis of radar sounding data face several technical challenges. 

These include uncertainties related to spatially variable attenuation losses and roughness scattering. As a result, applications of ice-penetrating radar have so far been limited to local-scale studies and mapping distribution of static water within and beneath the glaciers. 

In this talk, I will present novel methods where I combine ice-penetrating radar and numerical ice-sheet modeling to extract additional information from radar sounding data. I will demonstrate how we can apply this joint radar-model technique to gain new geophysical insights into the structure and dynamics of subsurface drainage systems in the Greenland ice sheet. 

I will delve into the importance of understanding the large-scale characteristics of these systems for the overall dynamics of ice sheets and their response to surface melting. 

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The School of Earth and Atmospheric Sciences Presents Dr. Joseph O'Rourke, Arizona State University

Vigorous fluid motions drive dynamos today in Earth and all major planets except Mars and Venus. Here, I will show how magnetic histories of rock/metal planets directly depend on conditions during their accretion and differentiation. 

In particular, giant impacts and planetary size and water content are always critical to dynamo energetics. Precipitation of magnesium oxide boosts the likelihood of dynamo activity in Earth and Venus, but hydrogenation of the core of Mars destroyed its dynamo. 

My future plans center on comparative planetology to understand fundamental interior processes that affect planetary atmospheres and surfaces. In parallel with computational geodynamics, I aim to develop spacecraft missions that provide ground truth for my models. To illustrate, I will present my proposed SmallSat mission to (2) Pallas—the largest unexplored protoplanet in the main asteroid belt and parent of many near-Earth asteroids.

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